We plan to continue our efforts to delineate the heme-binding site of hemopexin by chemical modification of the protein, to compare the metabolism of purified serum hemopexin and albumin in patients with aberrations of heme metabolism, and to complete an investigation on the effect of porphyrinogenic agents on the formation of bilirubin from heme in the isolated perfused rat liver. BIBLIOGRAPHIC REFERENCES: Conway TP and Muller-Eberhard U: Interaction of hemopexin with water-soluble porphyrins. Archives of Biochemistry 172:558-564 (1976). Morgan WT, Liem HH, Sutor RP, and Muller-Eberhard U: Transfer of heme from heme-albumin to hemopexin. Biochimica et Biophysica Acta 444: 435-445 (1976).